JavaFX intersection of shapes and polygons

Question

I'm currently working on intersect of bounds between different shapes with JavaFX. I would like to detect collision of two polygons on their points and not on their bounds (i.e. 2 polygons).

Please, see figure 1: not desired behavior, and figure 2: desired behavior.

Is there any existing algorithm to help me or any library to use? Thanks in advance :)

enter image description here

Here find my solution :

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Polygon;
import javafx.scene.shape.Shape;
import javafx.stage.Stage;

public class Tester extends Application {

@Override
public void start(Stage stage) throws Exception {
    Pane root = new Pane();
    root.setStyle("-fx-background-color:cyan;");
    Polygon p1 = new Polygon();
    p1.getPoints().addAll(new Double[]{
            50.,50.,
            50.,100.,
            60.,100.,
            60.,80.,
            80.,70.,
            80.,100.,
            100.,100.,
            100.,50.
    });
    p1.setFill(Color.GREEN);

    Polygon p2 = new Polygon();
    p2.getPoints().addAll(new Double[]{
            65.,100.,
            65.,90.,
            75.,80.,
            100.,100.
    });
    p2.setFill(Color.RED);

    root.getChildren().addAll(p1,p2);

    stage.setScene(new Scene(root));
    stage.show();

    Shape inter = Shape.intersect(p1, p2);
    root.getChildren().add(inter);

    System.out.println(inter.getLayoutBounds().getWidth() + ":" + inter.getLayoutBounds().getHeight());
    if(inter.getLayoutBounds().getHeight()<=0 || inter.getLayoutBounds().getWidth()<=0) {
        System.out.println("No intersection");
    }
    else {
        System.out.println("intersection detected");
    }
}

public static void main(String[] args) {
    launch(args);
}
}

Output:

enter image description here

20.0:16.0 intersection detected

It seems to work properly, I will test with Path objects to replace Polygon objets.

You might want to check if intersection points of the edges of one of your polygons is in bounds of the other. Use: `mypolygon1.getBoundsInLocal().contains(myPolygon2.getBoundsInLocal())` — Aspirant, Nov 27 '13 at 16:23
possible duplicate of [Checking Collision of Shapes with JavaFX](http://stackoverflow.com/questions/15013913/checking-collision-of-shapes-with-javafx) — jewelsea, Nov 27 '13 at 17:03
I tested Shape.intersect(...); and it seems to be ok. I update my example. — PacDroid, Nov 27 '13 at 18:10

score 1 · Answer 1 · edited Aug 28 '16 at 06:14

I was playing with your codes\, and I found this solution, I added mouse event to the polygon2, then I modified the if statement. If not too late, try.

public class Tester extends Application {

    Shape inter;
    Point2D pc;
    double initX, initY, mx, my;

    @Override
    public void start(Stage stage) throws Exception {
        Pane root = new Pane();
        root.setStyle("-fx-background-color:cyan;");
        final Polygon p2 = new Polygon();
        final Polygon p1 = new Polygon();
        p1.getPoints().addAll(new Double[]{
            50., 50.,
            50., 100.,
            60., 100.,
            60., 55.,
            80., 70.,
            80., 100.,
            100., 100.,
            100., 50.
        });
        p1.setFill(Color.GREEN);
        p2.getPoints().addAll(new Double[]{
            65., 100.,
            65., 45.,
            75., 80.,
            100., 100.
        });

        p2.setFill(Color.RED);

        p1.setTranslateX(400);
        p1.setTranslateY(250);

        p2.setOnMousePressed(new EventHandler<MouseEvent>() {
            public void handle(MouseEvent me) {
                initX = p2.getTranslateX();
                initY = p2.getTranslateX();
                pc = new Point2D(me.getSceneX(), me.getSceneY());
            }
        });

        p2.setOnMouseDragged(new EventHandler<MouseEvent>() {
            public void handle(MouseEvent me) {
                double dragX = me.getSceneX() - pc.getX();
                double dragY = me.getSceneY() - pc.getY();
                double newXPosition = initX + dragX;
                double newYPosition = initY + dragY;
                p2.setTranslateX(newXPosition);
                p2.setTranslateY(newYPosition);
                System.out.println("no intersection");
                if (Shape.intersect(p2, p1).getBoundsInLocal().isEmpty() == false) {
                    p1.setTranslateX(p2.getTranslateX() + mx);
                    p1.setTranslateY(p2.getTranslateY() + my);
                    System.out.println("colision");

                } else {
                    mx = p1.getTranslateX() - p2.getTranslateX();
                    my = p1.getTranslateY() - p2.getTranslateY();
                }

            }
        });
        root.getChildren().addAll(p1, p2);

        final Scene scene = new Scene(root, 1200, 850);
        stage.setScene(scene);
        stage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

score 0 · Answer 2 · answered Nov 27 '13 at 16:34

0

If you can use the java.awt.geom package in your application, I suggest you take a look at the Area class and especially the intersect method.

Basically you can do this:

area1.intersect(area2);
boolean areasintersect = !area1.isEmpty();

You can create arbitrary areas using the GeneralPath class in the same package.

answered Nov 27 '13 at 16:34

Sebastian

7,729
2
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no sorry I would like to use only JavaFX if possible, I'm diging into intersect methods for the moment, but thanks. – PacDroid Nov 27 '13 at 18:09
I have a question about this: Is it possible to convert a java.awt.geom Area class into a JavaFx Polygon? I have a swing app that I want to convert to JavaFx. Thanks. – Davem M Dec 19 '14 at 00:23
@DavemM That would be a new question, I would say. But the answer is probably: Only if the Area describes a polygon, in which case you would use `getPathIterator`, iterate over the shape and create the FX Polygon. – Sebastian Dec 19 '14 at 08:40

JavaFX intersection of shapes and polygons

2 Answers2